PROJECT SUMMARY ? TANGUAY PROJECT Polycyclic aromatic hydrocarbons (PAHs) are near ubiquitous contaminants at Superfund sites. Approximately 16% of the U.S. population, including ~17% of all children in the U.S. under the age of 5, live within 3 miles of a Superfund site. The physical proximity of so many people to PAH contamination challenges regulatory agencies to provide accurate risk assessments in order to protect public health. Human exposure to PAHs is complex; exposures always occur as complex mixtures rather than as individual parent PAHs. The potency for individual parent PAHs to produce adverse developmental outcomes is fairly well understood, but the additive antagonistic or synergistic effects of PAHs in mixtures is largely unknown. An added level of uncertainty is that PAHs are environmentally transformed, and the mobility and toxicity of these transformed PAHs can be significantly greater than the parent forms. Developmental exposure to PAHs may carry the greatest risk. Recent epidemiological data indicate strong associations between early life stage PAH exposures and the increased occurrence of birth defects and increases in significant neurobehavioral deficits and heart disease. Risk assessors desperately need of relevant in vivo data to develop comprehensive models for predictive toxicity. By linking biological responses to PAH structures, uptake, and diagnostic gene expression pathways, the Tanguay Project will establish zebrafish as a biosensor that can provide rapid feedback to SRP stakeholders responsible for risk assessment and remediation. This approach interrogates all aspects of development and the molecular pathways that underlie it, in one integrated experiment. We have developed an effective framework for conveying this high-impact work to stakeholders and for collaborating with populations to reduce their risk. Our overarching hypothesis is that we can learn to predict the toxicity of PAH mixtures based on the structural classes, bioactivity profiles and pathway targets of their PAH components. We will test this hypothesis in four Specific Aims: 1) Determine how the developmental impacts of PAH exposure depend on the composition of PAH mixtures, the chemical structures of environmentally transformed PAHs, and the presence of AHR signaling; 2) Measure the uptake and metabolism of biologically active PAHs in zebrafish; 3) Develop diagnostic gene expression pathways for classes of PAHs, determine how those pathways vary as a function of dose and associate those pathways with specific adverse effects; 4) Determine adult and transgenerational consequences of transient developmental exposures to individual PAHs and mixtures.